The present invention relates to Electrographic Recording apparatus. More particularly, it relates to an improved control means for electrographic recording apparatus.
Recently there has been developed an electrographic recording technology wherein the need for providing latent electrostatic images is eliminated. That technology is illustrated in Kotz, U.S. Pat. No. 3,816,840, Lunde, U.S. Pat. No. 3,879,737 and Lunde, U.S. Pat. No. 3,946,402, as well as in the above-noted copending application, Ser. No. 152,599. In accordance with the teachings in those patents, as well as in the copending application, a quantity of toner powder which has both electrical and magnetic properties is contained in a hopper position adjacent a drum made of non-magnetic material. Within the drum there is a magnet structure creating a magnetic field extending through the periphery of the surrounding drum. In one form of the structure disclosed, the drum rotates about an axis coaxial with the central magnet structure while the magnetic core is fixed. In another form, the outer drum is stationary while the inner magnetic core is rotated. In either case, the toner powder is drawn from a hopper by the magnetic field to be attracted to the outer periphery of the drum. The rotation of the drum or the magnetic core causes the toner particles to be translated around the periphery of the drum to a recording station. At the recording station, the recording medium, comprising a backing sheet such as paper having a dielectric coating thereon, is driven along a path spaced a small distance from the surface of the toner carrying drum. An electrically conductive element is positioned on the opposite side of the record member from the drum. Under the influence of the magnetic fields, the toner particles form whisker like strings about the surface of the drum. These whisker strings are of sufficient length to brush the surface of the record member. Because of the magnetic fields, these toner particles are not deposited upon a surface of the record receiving member unless an electric field is established between the drum or the electrodes carried by drum and the back-up conductive plate on the opposite side of the record member. When such electric fields are established, the electrostatic charges overpower the magnetic field influence and deposit the toner particles in selected areas on the record member in accordance with the pattern established by the electric fields.
In analogous embodiment shown in the aforementioned patents, a somewhat different technique is employed in that the record member is uniformally coated with toner powder and the unwanted portions of the toner powder is then picked off by the magnetic field, the desired portions being adhered to the record member by the superimposition of an electric field in the manner aforementioned. These improvements have thus provided a recording technique wherein records of data may be made without first imposing an electrostatic image on the record member which must then be developed by the toner. It is, in effect, a direct writing technique.
There is, in each of the systems heretofore described, a problem which has not been addressed. In each of the systems, when an end of recording has occurred the switches are turned off and the entire system comes to a stop including the recording and the paper drive mechanism. In either of the systems, when such system shutdown occurs, there is a quantity of loose toner on the record member which has not been "fixed" to the record member. Accordingly, in time, such unfixed toner creates both a messy condition within the recorder and has a tendency to fall off into the recording mechanism causing a potential jam situation.